The ability to visually perceive motion is believed to be highly beneficial for surviving in a dynamic environment. So it is not surprising to see that movement is one of the most important cues to attract visual attention. Interestingly, most mammals are able to perceive visual motion even if they are moving themselves—either by rotating the head, the eyes, moving the whole body or even while they are running. The gathered information is then used for controlling the own movement or for tracking moving objects by keeping them centred in the fovea.
In general, a robot's autonomous movement causes the camera to undergo translational and rotational movements in 3D with sudden velocity-changes.
The effects of Ego-Motion (EM) on the Optical Flow (OF), the so called ego-motion-flow (EMF), produced by a robot make this task quite challenging. Primarily, this is caused by the large number of degrees of freedom and the complex influence of each robot segment on the position of the camera: For example, bending the knee may in some situations cause the robot and hence the camera to shift and rotate violently to the side, whereas in other situations, the robot might be standing on the other leg and so knee bending does not affect the camera position at all.